1. Field of the Invention
The invention is based on a hydraulic regulating the brake pressure in a vehicle brake system.
2. Description of the Prior Art
For safety reasons, recent models of motor vehicles are as a rule equipped with a vehicle brake system that has anti-lock, traction control, and/or vehicle control programs. The key element of such vehicle brake systems is a hydraulic unit disposed in the vehicle. The hydraulic unit is able to regulate the brake pressure at one or more wheels of the vehicle automatically as needed, with the aid of an electronic control unit, and thereby to stabilize the vehicle. The control unit to that end evaluates signals of sensors in the vehicle and triggers hydraulic components disposed on the hydraulic unit electronically accordingly.
In the prior art, a vehicle brake system with driving stability control is well known. See the brochure published by Robert Bosch GmbH, entitled “Fahrstabilisierungssysteme” [Driving Stability Systems], page 90, FIG. 3, which appeared in the “Gelbe Reihe, Ausgabe 2004” [“Yellow Series, 2004 Edition”], ISBN 3-7782-2026-8. To aid in understanding the invention, the circuit diagram disclosed there is appended as FIG. 1 and will now be described briefly:
The known vehicle brake system includes a driver-actuated master cylinder 10 for generating a brake force by muscle power. Connected to the master cylinder 10 are two separate brake circuits 12, 14, each with two wheel brakes 16, 18; 20, 22. For individual-wheel regulation of the brake pressure, there is a hydraulic unit 24. It is connected between the master cylinder 10 and the wheel brakes 16-22 and has different hydraulic components. Each wheel brake is preceded by a respective inlet valve 26 and followed by a respective outlet valve 28. The inlet valves 26 control a brake pressure buildup and the outlet valves 28 control a brake pressure reduction at the associated wheel brakes 16-22. One pump 32 per brake circuit, which can be driven by an electric motor 30, is capable of aspirating brake fluid out of the associated wheel brake 16-22 via one of the outlet valves 28 for brake fluid reduction and pumping it into the brake circuit 12, 14. To enable making a fast brake pressure buildup, a low-pressure reservoir 34 is connected between the outlet valves 28 and the pump 32 of one brake circuit 12, 14. Between the pump 32 and the low-pressure reservoir 34, there is a check valve 36 that closes in the direction from the pump 32 to one of the wheel brakes 16-22. This valve prevents the underpressure on the intake side of the pump 32 from being propagated into one of the wheel brakes 16-22.
Each brake circuit 12, 14 furthermore has a high-pressure on-off valve 38 and a reversing valve 40. The high-pressure on-off valve 38 makes it possible for the pump 32, as needed, to aspirate necessary additional brake fluid directly from the master cylinder 10. The reversing valve 40, in the event of its actuation, can block a pressure fluid connection from the wheel brakes 16, 18; 20, 22 of a brake circuit 12, 14 with the master cylinder 10. This is necessary in case brake pressure at one of the wheel brakes 16-22 is supposed to be automatically built up regardless of what the driver is asking for. This situation occurs during a traction control operation and/or driving stability control operation.
Moreover, check valves 42 are provided for controlling bypass conduits around the inlet valves 26 and the reversing valves 40. Thus a reduction of brake pressure is made possible even if the inlet valves 26 are closed, and a buildup of brake pressure is made possible if the reversing valves 40 are closed, or in other words during a traction control or driving stability control operation that is taking place. Line connections are also embodied on the hydraulic unit 24 in order to put the aforementioned components 26-42 into hydraulic contact with one another. These line connections are represented in the schematic illustration by straight connecting lines.
The invention to be described below is based on embodying this known hydraulic circuit diagram in an especially space-saving way that is easy to achieve in the production of a housing block of a hydraulic unit 10.